In a foundry, molten metal that has been melted in a furnace, etc., and that is hot, is transported to a pouring machine. It is poured into a mold by the pouring machine so that a product is cast. Depending on the property of the cast iron to be produced, an alloyed metal, such as Mg, Ce, Ca, Ni, Cr, Cu, Mo, V, or Ti, may be added to the molten metal to improve the strength and toughness, corrosion-resistance, heat-resistance, or abrasion-resistance. Generally, the alloyed metal is preliminarily put in a ladle that is to receive molten metal from the furnace so that it reacts with the molten metal that is poured into the ladle. Here, both molten metal that has not yet reacted with the alloyed metal, i.e., that is melted in a furnace, etc., and molten metal that has reacted with the alloyed metal, are just called “molten metal.”
The reaction of the molten metal with the alloyed metal is usually violent. To improve the yield, the depth of the ladle should be 1.5 to 2.0 times its diameter. Thus a ladle for a reaction (hereafter, “ladle for reaction”) that is deep and that has a pocket to store an alloyed metal is used. Further, it is transported into a room for a reaction to diminish the effects of the reaction on the environment. The molten metal that has reacted is transferred from the ladle for reaction to a ladle for pouring by means of a crane, etc., so that it is transported to a pouring machine that pours the molten metal into a mold. Thus such a ladle for reaction is also called a ladle for transferring. Transporting hot molten metal by means of a crane, etc., and transferring it from the ladle for reaction to the ladle for pouring require dangerous operations.
Therefore, a line for transporting molten metal has been proposed, wherein the molten metal is transported and transferred (see Japanese Patent No. 5475004). It comprises a bogie for transporting and transferring the molten metal that transports the ladle for receiving the molten metal on a track, a means for moving the ladle in the direction that is perpendicular to the track, a mechanism for vertically moving the ladle on the means for moving the ladle, a means for tilting the ladle that is provided on the mechanism for vertically moving the ladle, and a device for holding the ladle that is tilted by means of the means for tilting the ladle and that releasably holds the ladle for receiving the molten metal.
For example, to produce ductile cast-iron a spheroidizing element, such as Mg, Ce, or Ca, which is the alloyed metal, is added to the molten metal. The spheroidizing element is depleted over time, since it reacts with refractory materials of the ladle or air. Namely, fading of the spheroidizing element (below, simply called “fading”) occurs. The fading is a phenomenon where the effect of a graphite-spheroidizing agent fades over time after the agent is added to the molten metal. Typically, it fades 20 minutes after it is added. If the effect fades, spheroidizing may become poor. Thus pouring the molten metal into a mold must be completed before poor spheroidizing by fading occurs.
Conventionally, the time for fading has been calculated by a skilled person so that poor sphedoidizing is prevented. However, the time for fading depends on the kind and the amount of the alloyed metal. Further, it may also depend on the size of a ladle for reaction and the method for transporting the ladle (the vibration of the ladle for reaction). The alloyed metal that has been manually measured is put into the pocket of the ladle for reaction by an operator. The operator causes the ladle for reaction to be quickly transported to the front of the furnace, causes the molten metal to be received by the ladle to spheroidize it, and causes the molten metal to be transferred to the ladle for pouring. By this way, the operator must work near the ladle for reaction that contains the molten metal. Thus problems in the working environment and safety have been pointed out.
As discussed above, in the foundry the following device or equipment may be installed: 1) equipment for melting, such as a furnace, 2) a device for feeding an alloyed metal, 3) a machine for pouring molten metal into a mold, 4) equipment for transporting the ladle for reaction among the position of the device for feeding an alloyed metal, the position of the furnace, the position of the room for a reaction, and the position for transferring the molten metal to the ladle for pouring, and 5) equipment for transporting the ladle for pouring between the position for transferring the molten metal from the ladle for reaction and the position of the machine for pouring molten metal into a mold. Since the foundry is wide and each of the devices and the equipment may be replaced individually, the controllers are installed for the respective devices and equipment. However, for example, although fading starts in the ladle for reaction, the effects of the fading must be considered at the operation for pouring the molten metal in the ladle for pouring into a mold.
The present invention aims to provide a system and a method for transporting molten metal to automatically feed an alloyed metal to a ladle for reaction and to automatically transport molten metal from the ladle for reaction to the pouring machine so as to safely produce a cast product that has stable qualities.